Approach control apparatus



June 9, 1942. L. R. ALLlscN A 2,285,881

APPRoAcHcoNTRoL APPARATUS Filed .June 11, 1941 Fig] l; 4T f 51' j 6T f L 2 56'/ @2C Fly? lla

T AR B 5m wg -J g 0 Jzlgnal- Jelec'tzbn eazls'z'ancehzm 5 pamtus INV NTOR Leslz .Allison 2Carrelli Amperes HIS ATTQRNEY Patented June 9, 1942 s APPROACH CONTROL APPARATUS 'Leslie`R. Allison,`.Forest Hills, Pa., assigner to The Union Switch '& Signal Company, Swissvale, Pa., a-corporation -of Pennsylvania .Application June 11, 1941, Serial No. 397,581

Claims.

My invention relates to improved 'approach control apparatus for use in railway signaling systems.

It has heretofore been `proposed to .have at the exit end of a section of railway :track an approach control relay connected in .serieswith the track .battery for the .track section. In such systems the various parts of the .equipment are selected and adjusted so that when the track section is vacant too little energy ows .in the circuit of theapproach control relaytopick up this relay, or to keep it picked up, and .accordingly its contact is released and interrupts the circuit of the lamps vof the signal .for the ,adjacent track section in advance ito thereby normally keep `this ,signal jdark.

In such systems thevarious parts ofthe equipment lare selected and adjusted so that when a train enters the track section the ourrentflowing in the track circuit, and in the approach control relay, is increased toa degree su'icient to pick up Athis relay so that its contact establishes `the circuit of the .lamps of the signal of the adjacent section 4in advance so that these lamps are lighted to indicate tothe engineer of the approaching train -the nature of .traic conditions in advance.

In the systems of this type heretofore employed it has been diicultpr impossible to proportion and adjust the parts ofthe apparatus so that the system will function reliably .under different conditions lof ballast resistance and track battery voltage. In these systems, vif the equipment were adjusted to insure that the approach relay would pickup before thetrain advanced too close to the signal 'at timeswhen the battery voltage is low andthe ballast resistance A'is high, the relay might fail to release after the train vacates the section at times when the battery voltage is high l'and the ballast resistance is low. Because of the low ratio of release to pick-up values of the `approach relays this problem is particularly difficult in track sections yemploying steadyenergy in the track circuit.`

It is an object of `this invention *to provide an improved approach control system of the type described which is Yarranged 'so `that operation of the approach control relay is more positive and certain.

A further object ofthe `invention is to provide a system of the 'type described and incorporating means for increasing the diierence which exists in the voltage across the relay `terminals when the section is occupied and Vwhen the section is vacant.

Another object of the invention is l'to-provide an improved approach control system.

I shall describe three forms of improved approach control apparatus embodying my invention, and shall then point out thenovel features thereof in claims.

In the drawing Fig. l is a diagram of a section of railway track employing steady energy in the `track circuit thereof and equipped with approach control apparatus provided by this invention,

Fig. 2 is a fragmentary diagram Ishowing a modification which I may employ,

Fig. 3 isa diagram of asection of railway track employing coded energy in the track circuit Athereof and equipped with approach control apparatus provided by this invention, and

Fig. 4 is a diagram showing the operating characteristics of the ballast lamp employed in this invention.

Similar reference characters refer to similar parts'in each of the various views.

`Referring to Fig, 1 there is shown therein a stretch of railway track having a pair of `track rails l Aand 2 over which traffic normally moves in the direction indicated by the arrow, that is, from left to right. The rails l and 2 are divided by insulated Ajoints into the customary successive track sections. One such section is shown and is designated 5T, while the adjoining sections are designated 4T and 6T.

Each of the track sections has at the entrance end thereof a wayside signal S for indicating to approaching trains the nature of traffic conditions in advance. As shown these signals are of the color light type having a red or stop lamp R, a yellow or caution lampY, and a green or clear lamp G. While the color light type of signal has been illustrated the invention is not limited to use with signals of `this type but is equally applicable to all forms of wayside signals.

Similarly, while the approach control apparatus provided by this invention is illustrated and described in connection with control ofthe lighting of wayside signals the invention is not limited to use for this purpose but may be used wherever apparatus of `this type is desired.

Each track section is provided with means for controlling the signal 'for that section in accordance with traffic conditions in that section as well as in advance. The means for controlling the signals is not a part of this invention, and any means well known in the art may be lemployed for this purpose.

Each track section is provided with means for detecting the presence of a train in the section. This means comprises a track circuit including a track battery TB at the exit end of the track section and a track relay TR at the entrance end of the track section. The equipment at the exit end of the section includes, in addition, an approach control relay EAR, a resistance device in the form of a ballast lamp 5BL, and resistors I, II and I2. One terminal of the battery TB is connected to track rail I, while the other terminal of the battery is connected to track rail 2v in series with the ballast lamp SBL and resistor III. One terminal of the winding of the relay SAR is connected to one terminal of the ballast lamp BL, while the other terminal of the winding of relay EAR is connected in series with resistor II to the other terminal of the ballast lamp 5BL. The resistor I2 is connected across the terminals of the winding of the relay EAR. The resistance device or ballast lamp BL is of a type well known in the art and consists of a length of iron or other wire in a sealed envelope. The operating characteristics of the lamp are shown graphically in Fig. 4 of the drawing Which shows the resistance of the lamp when current ci different values is supplied through the lamp.

As shown in Fig. 4 the resistance of the lamp remains substantially constant until the current flowing through the lamp is increased to a predetermined degree, While on a further increase in the current iiowing through the lamp the resistance of the lamp increases very rapidly.

When the track section is vacant energy from the track battery is supplied over the track rails I and 2 to the track relay ETR. The energy supplied to the track circuit is supplied through a plurality of paths. One of these paths is: traced from one terminal of the battery through the ballast lamp BL and the resistance I to track rail 2. A second path shunting the ballats lamp BL and including the resistance I I is provided. The second path has two branches, one of which includes the winding of relay SAR and the other of which includes resistance I2.

The resistance I 0 provides means to adjust the total track circuit current to a value effective to pick up the track relay without taking excessive energy from the track battery. The resistance I I makes it possible to apportion the track circuit lenergy between the path which includes the ballast lamp BL and the path shunting this lamp, while the resistance I2 makes it possible to regulate the proportion of thecurrent in the shunt path which is supplied through the winding of the approach relay AR.

The various parts of the equipment are selected and proportioned so that when the section is vacant, the ballast resistance is low and the track battery voltage is high the current supplied through the ballast lamp BL isv somewhat less than the value indicated at X in Fig. 4. The various parts of the apparatus are also selected and adjusted so that when the track section is vacant sufficient energy is supplied to the track relay to pick up its contacts, while insuiiicient energy is supplied to the winding of the approach relay AR to pick up the contacts of this relay.

At this time, therefore, the track relay 5TR is picked up to condition signal 5S to provide a proceed indication, while contact I4 of approach relay SAR is released and interrupts the circuits of the lamps of signal GS so that neither of these lamps is lighted.

When a train moving in the normal direction of traffic enters section 5T the track relay STR is shunted and its contacts release to cause signal 5S to provide its red or stop indication. At this time the Wheels and axles of the vehicles forming the train provide a low resistance path between the track rails so that there is an increase in the energy supplied from the track battery TB to the section rails.

On this increase in the current iiow there is some additional flow of current through the ballast-.lamp BL and in the path shunting this lamp.

As the train advances in the track section the length of the track rails included in the track circuit is reduced and there is a corresponding reduction in the 'resistance of the track circuit and a further increase in the flow of current from the track battery to the track rails.

The various parts of the equipment are arranged and proportioned so that as a result of entrance of the traininto the section and its advance in the sectionv the current in the lamp is increased somewhat above the value indicated at X in Fig. 3. The current in the lamp, therefore, is in the range in which the resistance of the ballast lamp increases much more rapidly than the current supplied through the lamp. Accordingly most of the increased track circuit energy is supplied through the path shunting the ballast lamp and the increase in the current in the winding of the approach relay is proportionately greater than the increase in track circuit current. This insures that under varying conditions of track ballast resistance and track battery voltage the current in the approach relay will be increased to a value high enough to pick up the relay contact before the train advances all the way to the exit end of the section.

The various parts of the equipment are also proportioned so that when the train advances to a predetermined point in the track section, such as a point 4000 feet from the end of the section, the energy in the circuit of the approach relay AR is increased to an extent sulicient to pick up the contact I4 of the relay to Vthereby establish the circuit of one or the other of the lamps of signal BS.

When the train passes out of the track section the current in the track circuit is reduced to its normal level and is insui'icient to maintain the contact I4 of approach relay AR picked up.

On this reduction in the current in the track circuit there is a reduction in the current flowing through the ballast lamp BL and also in the current in the path shunting this lamp. On this reduction in the current in the lamp there is a decrease in the resistance of the lamp. This decrease in the resistance of the lamp is proportionately greater than the decrease inthe current in the track circuit with the result that the decrease in the current in the circuit of the winding of the approach relay AR is proportionately greater than the decrease in track circuit current. This insures that when the train vacates the track section the energy in the winding of the approach relay will be reduced to a value such that the approach relay AR will be certain to release and its contact I4 will interrupt the circuits of the lamps of signal BS.

From the foregoing it will be seen that when the current in the track circuit is changed as a result of changes in trailic conditions in the track section the ballast lamp causes the changes in the current in the approach relay to be magnied, 'I'his insures that the approach relay will pickup and-establish 1the 1circuits o'I `the signallamps when a Vtrain advances to a predetermined point `in the ftrack section, whileit further insures that the approach Vrelay will i release 9when the track section is vacated.

In Fig. .2 Athere isshown a modiedcircuit arrangement 'which 4may vbe employed 'in place of thatshown in Fig. 1. In the -modicationshown in one terminal offthe trackbatteryisconnected to track rail '2 `through the ballast lamp BL andthe-resistance lea, while'this terminal of the -fbattery is `also lconnected vto track rail 2 through the-resistance Ll la. The approach relay AR is connected across a fportion of the -resistance Ha.

The resistance -|a maybe adjusted so that when Athe track sectionisvacant kthe energy supplied `to the track circuit Athrough the ballast lamp lBL'is slightlyless thanthe `value indicated at 'Xin Fig. 4. The resistance H'a `may be =ad `just-ed so that lenough energy in addition to that supplied through #the ballast lamp BL `will 'be supplied -to the track circuit to properly operate the track relay, `while lthe 'winding of the -approach relay Vcan -be connected across such'a portion of resistance Ha that insufficient energy is supplied through the relay winding when -the `track section is vacant to operate the relay.

In operation the modication shown in Fig. 2 is-similar to that shown in Fig. l and a detailed explanation of its operation is unnecessary.

The modification shown in Fig. 3 shows the application of the invention to a track section employing coded current in the track circuit thereof. that shown in Fig. 1 and diiiers therefrom in that a coding device CR is included in the circuit of the track battery, While the approach relay AR and the track relay TR are of the code following time. A slow release repeater relay AP is provided for the approach relay AR and governs the circuits of the lamps of signal SS.

The various parts of the equipment of the modiiication shown in Fig. 3 are selected and adlusted so that when the track section is vacant suflicient energy is supplied over the track circuit to cause the track relay TR to follow the coded energy supplied over the track rails. The equipment is also arranged so that when the section is vacant the energy supplied through the ballast lamp BL is below the value indicated at X in Fig. 4, while the energy supplied through the winding of approach relay AR is insuilicient t0 pick up the contact of this relay.

When a train enters the section there is an increase in the value of the impulses of coded energy supplied to the track rails and when the train reaches a predetermined point in the track section the current owing in the approach relay AR is suflicient to cause code following Operation of this relay. Accordingly, contact I6 of relay7 SAR intermittently establishes the circuit of relay EAP and contact I1 of relay EAP picks up and establishes the circuit of the lamps of signal SS. The relay AP is slow enough in releasing for the contact Il' to remain picked up during the intervals between the supply of impulses of energy to the relay.

As coded energy is employed in the modication shown in Fig. 3 the contact of the relay SAR releases during each 01T interval in the code, while it picks up during each on interval in the code. Because of the action of the ballast lamp BL, when the section is occupied the in- The circuit shown in Fig. 3 is similar to crease in the value of the current in the Winding -fof `the approach relay AR .is l:proportionately greater than the increasefin the value ofitheii-m.w pulses o'f energy :supplied to vthe :track circuit. Accordingly, :operati-on of the Aapproach relay `4is more positive than would 'be the 4case if fthe sballastllamp .Were-not provided.

fIn addition, because of the .fballast lamp the circuit may be #adjusted to provide proper operation :of 'the approach relay `when the section is occupied -Witha smaller totalcurrent suppliedito the track circuit than would be required if .the ballast lamp were not=employed- Although I have herein illustrated .and .described three 'forms of approach control lapparatusembodying my `invention, itis understood that various changes :and `modifications may be made therein Within :the scope .of the appended claims without departing from vthe spirit and scope of `my invention.

Having fthus described my invention, what I claim is:

1. 'In combination, :a section of railroad track having `a pair vof Atrack rails 'over which -trafiic normally moves lin one direction, ia ftrack relay connected across the-section rails at'the entrance end of the section, a tra-ck battery, fa resistance device and an approach lrelay atthe'lexitlend-of the track section, means for connecting -the track battery across the section rails in --series with the Winding of the approach relay, and means for lconnecting the `track rbattery across the section rails in series with said resistance device so that the resistance device and the approach relay winding are connected in parallel, said resistance device having operating characteristics such that its resistance increases rapidly on an increase in the ow of current therethrough, whereby on entrance of a, train into the section and resultant increase in the supply of energy `from the track battery to the track rails a relatively large proportion of the increase in current flow occurs through the connection including in series therewith the winding of the approach relay.

2. In combination, a section of railroad track having a pair of track rails over which traflic normally moves in one direction, a track relay connected across the section rails at the entrance end of the section, a track battery, a resistance device and an approach relay at the exit end of the track section, means for connecting one terminal of the track battery to one track rail in series with the resistance device and the approach relay in multiple, and means for connecting the other terminal of the battery to the other track rail, said resistance device having operating characteristics such that its resistance increases rapidly on an increase in the flow of current therethrough, whereby on entrance of a train into the section and resultant increase in the supply of energy from the track battery to the track rails a relatively large proportion of the increase in current flow occurs through the connection including in series therewith the winding of the approach relay.

3. In combination, a section of railroad track having a pair of track rails over which traino normally moves in one direction, a track relay connected across the section rails at the entrance end of the section, a track battery, a resistance device and an approach relay at the exit end of the track section, means for connecting one terminal of the track battery to one track rail in series with the resistance device and the approach relay in multiple, and means for connecting the other t'erminal of the battery to the other tra'ck rail, means for adjusting the total energy supplied from the track battery to the section rails when the section is unoccupied to a value effective to -pick up the track relay but ineffective to pick up the approach relay, said resistanc-e device having operating characteristics such that its resistance increases rapidly on an increase in the flow of current therethrough, whereby on entrance of a train into the section and resultant increase in the supply of energy from the track battery to the track rails a relatively large proportion of the increase in current flow occurs through the connection including the winding of the approach relay in series therewith so that the approach relay Will pick up when the section is occupied and will release when the section is vacated.

4:. In combination, a section of railroad track having a pair of track rails over which trafiic normally moves in one direction, a track Arelay connected across the section rails at the entrance end of the section, a track battery, a resistance, and a resistance device at the exit end of the section, means for connecting one terminal oi the track battery to one track rail in series with the resistance and the resistance device in multiple, means for connecting the other terminal of the track battery to the other track rail, and an approach relay having its winding connected in multiple with a portion of said resistance, said resistance device having operating characteristics such that its resistance increases rapidly on an increase in the iiow of current therethrough, whereby on entrance of a train into the section and resultant increase in the supply of energy from the track battery a relatively large proportion of the increase in current flow occurs through the connection including the resistance in series therewith so that there is a corresponding relatively large increase in the flow of current in the winding of the approach relay.

5. In combination, a section of railroad track having a pair of track rails over which traffic normally moves in one direction, a track relay connected across the section rails at the entrance end of the section, a track battery, a resistance device and an approach relay at the exit end of the track section, means for connecting one terminal of the track battery to one track rail in series with said resistance device and a rst adjustable resistor, means for also connecting said battery terminal with said one track rail in series with a second adjustable resistor, and means for adjustably connecting the Winding of the approach relay across a portion of said second resistor, said resistance device having an operating characteristic such that its resistance increases rapidly on an increase in the flow of current therethrough.

LESLIE R. ALLISON. 

